Clock system



INVENTOR.

2 Sheets-Sheet Q9 5 ow CLOCK SYSTEM R. M. DURIS mm w@ E. n v oof om w mmJune 27, 1967 Original Filed June 16, 1964 June 27, 1967 R. M. DURIS3,327,324

CLOCK SYSTEM Original Filed June 16, '1964 2 Sheets-Sheet v INVENTOR.

RUDOLPH M. DURIS QMJWLWLZM A TTORNEYS United States Patent 3,327,824CLOCK SYSTEM Rudolph M. Duris, South Norwalk, Conu., assignor to EdwardsCompany, Inc., a corporation of Connecticut Original application June16, 1964, Ser. No. 375,492, now

Patent No. 3,282,043, dated Nov. 1, 1966. Divided and this applicationApr. 12, 1966, Ser. No. 559,022 I 4 Claims. (Cl. 192-84) Thisapplication is a division of copending application, Ser. No. 375,492,filed June 16, 1964, now U. S. Patent No. 3,282,043.

The present invention relates to systems of electric clocks employingsynchronous motors and more particularly, to such systems in which theelectric clocks are automatically reset after there has been an electricpower interruption.

In accordance with the present invention, a unique downtime accumulatoris provided which measures the length of time of an electric powerinterruption and resets the electric clocks of the system to the correcttime when the electric power returns. This downtime accumulator includestwo cams with a mechanical clock movement drive and a synchronous motordrive. When there is a power interruption, the mechanical clock movementdrive is coupled to the cams by an electromagnetic clutch to rotatethecams so that the cams orientation at all times represent the amountof time the electric clocks are in error due to the interruption ofelectrical power. When power is returned after .the interruption, theelectromagnetic clutch disconnects the synchronous motor drive to thecams. At the same time, electric current is fed through switch meanscontrolled by the cams to the synchronous motor drive and to asynchronous motor in each of the electric clocks of the system. Thiscauses the synchronous motor drive to rotate the cams toward theirorientation when the electrical power failed and causes the mentionedsynchronous motor in each electric clock to correct the error whichaccumulated during the power interruption. When the cams reach theirorientation at the start of the power failure, the electric clocks againindicate the correct time and the cams open up the switch to stop theelectric current flow to the synchronous motor drive and to thementioned synchronous motor in each electric clock.

Of particular importance in obtaining accurate operation of the abovedescribed downtime accumulator is the unusual electromagnetic clutchemployed in transferring the drive for the cams from the output of themechanical clock mechanism to the output of the synchronous motor. .Thisclutch has one plate with a number of closely spaced radial grooveswhich by energizing and deenergizing the clutch are contacted with andseperated from a number of soft rubber sleeves, mounted on armsextending from a second plate; It has been found that this arrangementdoes not permit slippage between the two plates while transmittingmotion to the cams, and there is no tendency for either of the plates tocause the other plate to jump upon engagement. H

In the preferred embodiment, the clock system has a master clock. Likethe other clocks in the system the master clock is normally driven by asynchronous motor. However, unlike the other clocks in the system, whenthe power fails the master clock is driven by the mechanical clockmovement so that at all times the hands of the master clock willindicate the correct time. This is accomplished with additionalelectromagnetic clutches of the type described above, which change thedrive for the master clock from the synchronous motor to the mechanicalclock movement when there is a power interruption and then return thedrive for the clock to the synchronous motor when power is resumed.

These and other features of the present invention may be best understoodby reference to the accompanying drawings of which:

FIGURE 1 is a schematic diagram of the preferred form of the invention;

FIGURE 2 is the clutch plate with the radial grooves; and

FIGURE 3 is the clutch plate with the soft rubber sleeves.

In the preferred form of the invention, the minute and hour hands ofeach of the electric clocks 10 of the system are connected to twosynchronous motors 12 and 14 through a shaft 16 while the second hand ofeach of the electric clocks 10 is connected to only one of the twomotors, motor 12, through a shaft 18. g The motors 12 and 14 areidentical shaded pole motors with light weight rotors that rotate at3600 r.p.m. and are geared down for driving the hands of the clock. Themotor 12 is geared down 3600 to 1 and coupled to the shaft 16 throughdifferential 20 and to the shaft 18 directly so that the motor 12 turnsboth the shafts 16 and 18 at one revolution a minute when the motorsfield 22 is excited. The motor 14 is geared down 400 to 1 and coupled tothe shaft 16 through the differential 20 so that the motor 14 rotatesthe shaft 16 at nine revolutions a minute when its field 24 is eXcie-d.The difference between the gearing of the motors 12 and 14 isrepresented in FIGURE 1 by gear box 26.

In normal operation of the electric clocks 10, the field 22 of motor 12is connected across the 115 volt 60 cycle line while the field 24 iskept open to keep the motor 14 unenergized. However, when the electricclocks 10 are slow, the field 24 can be connected in parallel with thefield 22 across the 115 volt 60 cycle line so that the electric clockswill run at ten times their normal speed until the electric clocks againindicate the correct time. The present invention provides a new masterclock and clock error correction system to be used with the aboveelectric clocks 10 to keep the correct time on a master clock duringinterruptions of the electrical power and to automatically restore theelectric clocks 10 to the correct timeafter the resumption of electricalpower.

This master clock and error correction system has a master clock face 28for displaying the correct time at all times and, has a normally openswitch 30 to connect the windings 24 for the motors 16 across the 115volt cycle line to correct the electric clocks 10 when they are slow.

During normal operation of the electric clocks 10, the hands on themaster clock face 28 are driven by a synchronous motor 34 which is thesame as synchronous motors 12 and 14, of the electric clocks 10. Also,the switch 30 is open to keep the motors 14 of the electric clocks 10stationary. When the current to the electric clocks 10 .is interrupted,the hands of the master clock face 28 are drivenby a mechanical clockmovement 36. Whenthe current is restored to the electric clocks 10 afterthe interruption, the synchronous motor 34 again drives the hands on themaster clock face 28, and the switch 30 is closed so that the motors 12and 14 drive the hands of the system clocks together at ten times theirnormal rate to make up the error which occurred during the powerinterruption. After the hands of the system clocks 10 indicate thecorrect time again, the switch 30 is opened to return the system tonormal operation.

The transfer of the drive for the hands of master clock face 28 betweenthe synchronous motor 34 and the mechanical clock movement 36 and theopening and closing of the switch 30, is accomplished by a uniquemechanism employing three meshed gears 44, 46 and 48 and threeelectromagnetic clutches 38, 40 and 42 which are energized while currentis supplied to the electric clocks and are deenergized when the currentsupplied to the electric clocks is interrupted.

The first meshed gear 44 drives the hands of the master clock face 28through chain drive 50 having two sprockets 52 and 54 and a drive chain56. One sprocket is centrally mounted on the gear 44 for rotationtherewith. The other sprocket 54 is mounted on the drive shaft 58 of thehands of the master clock face 28. The chain 56 meshs with the twosprockets 52 and 54 to transmit the movement of the gear 44 to the shaft58 to drive the hands of the master clock face 28.

The first meshed gear 44 is coaxially mounted around the output shaft 60of the mechanical clock movement 36 and is free to rotate with respectto said shaft 60 during normal operation of the electric clocks 10.However, during periods in which the electrical power is cut off fromthe electric clocks 10, the gear 44 is fixed to the mechanical clockmovements output shaft 60 to transmit the rotation of the shaft 60 tothe drive shaft 58 for the hands of the master clock face 28.

To couple and uncouple the shaft 60 to and from the gear 44, the firstmagnetic clutch 38 is employed. The magnetic clutch 38 has aparamagnetic plate 62 which is fixed to the shaft 60 and has clutchingsurfaces 64 fixed to the first meshed gear 44.

While current is being supplied to run the electric clocks 10, the plate62 is held out of engagement with the clutching surfaces 64 and againstthe paramagnetic frame 66 of the clutch by the magnetic field set up inthe paramagnetic frame by the energized coil 68 of the clutch. Thisleaves the first meshed gear 44 free to rotate with respect to the shaft60 while, as shall be seen hereafter, the first meshed gear 44 is beingdriven through the second meshed gear 46 by the synchronous motor 34.

When the current to the electric clocks 10 fails, the coil 68 isdeenergized and releases the plate 62 allowing a spring 70 positionedbetween the paramagnetic frame 66 and the plate 62 to force the plate 62into engagement with the clutching surfaces 64. This fixes the outputshaft 60 of the mechanical clock mechanism 36 to the first meshed gear44 so that the mechanical clock mechanism will drive the first meshedgear 44 and, through the first meshed gear 44, the hands of the masterclock face 28.

While electric current is being supplied to run the electric clocks 10,the synchronous motor 34 drives the first meshed gear 44 through thesecond meshed gear 46. A shaft 72 connected to the synchronous mot-or 34passes axially through the second meshed gear 46 and, on the other sideof the second meshed gear 46, is fixed to a paramagnetic plate 74 facingthe second electromagnetic clutch 40. Also, fixed on the shaft 72 arethe clutching surfaces 76 of the clutch.

While current is supplied to run the electric clocks 10, the magneticfield set up in the paramagnetic frame 78 of the clutch 40 by the coil80 mounted within the frame draws the plate 74 to the frame 78. Thiscauses the shaft 72 to move along its axis and bring the clutchingsurfaces 76 in contact with a disc 82 coaxially fixed to the secondmeshed gear 46. Therefore, when power is on, the synchronous motor 34drives the hands of the master clock face 28 through shaft 72, theclutching surfaces 76, the plate 82, the second meshed gear 46, thefirst meshed gear 44, and the chain drive 50.

When there is an interruption in the current to the electric clocks 10,the coil 80 of the second clutch 40 is deenergized allowing a spring 84mounted between the frame 78 and the plate 74 to force the plate 74 awayfrom the frame 78. This disengages the clutching surfaces '76 from thedisc 82 permitting the second meshed gear 46 to rotate freely of thesynchronous motor 34 while the first meshed gear 44 is being driven bythe mechanical clock movement 36.

In addition to meshing with the first meshed gear 44; the second meshedgear 46 also meshes with the third meshed gear 48 to transmit therotation of the first meshed gear 44 to the third meshed gear 48. Thethird meshed gear is mounted coaxially on the shaft 86 of two earns 88and 90 which control the opening and closing of the switch 30. Theswitch 30 is connected in between the 115 volt 6O cycle line and thefields 24 of the synchronous motors 14 for the electric clocks 10'sothat when the switch 30 is closed the synchronous motors '12 and 14together drive the hands of the systems clocks 10 at ten times theirnormal speed.

The cams 88 and 90 are circular cams each having a single detenttherein. A cam follower 92 is fixed to the switch 30 and rides on theperiphery of the cams 88 and 90 as they rotate. When the cam follower 92rides on the periphery of either cam 88 or 90 it holds switch 30 closedallowing current to reach the coils24 of the synchronous motors 14. Whenthe cam follower 92 is simultaneously positioned in the detents of boththe earns 88 and 90, the circuit between the 115 volt 60 cycle line andthe coils 24 of the motor 14 is opened by the switch preventing currentfrom reaching the coils 24.

One of the cams 90 is fixed coaxially to the shaft 86 so that it rotatesdirectly with the shaft 86. The other of the cams 88 is positioned on asleeve 94 mounted on the shaft and is therefore free to rotate withrespect to the shaft 86. This second cam 88 is driven through a geartrain 96 by the shaft 86 so that it rotates at the speed of the cam 90.Therefore, the cams 88 and 90 rotate in the same relation as the minuteand hour hands of the clock, that is, cam 88 makes one revolution forevery 12 revolutions of the cam 90.

Fixed to the cam shafts 86 is a paramagnetic plate 98 which faces theparamagnetic frame 100 of the third electro-magnetic clutch 42. Alsofixed to the cam shaft 86 are clutching surfaces 102 which face inopposite directions towards the third meshed gear 48 and a plate 104axially fixed to a sleeve 106 on which is mounted another gear 108. Whenthe coil 110 of the clutch 42 is deenergized, a spring 112 mountedbetween the paramagnetic frame 100 and the plate 98 forces the plate 98away from the frame 100. This brings the clutching surfaces into contactwith the third meshed gear '48 so that the third meshed gear 48 drivesthe shaft 86. Since all the clutches are deenergized at the same time,this means the mechanical clock movement 36 will drive the shaft 86through the plate 62, the clutching surfaces 64, the three meshed gears44, 46 and 48, and the clutching surfaces 102. The mechanical clockmechanism 36 therefore causes the cams 88 and 90 to be rotatedclockwise. As will be shown later, the cams are normally positioned sothat the cam follower 92 is in the detents of both the cams 88 and 90.When the mechanical clock rotates the cams, they will be rotated awayfrom this detent position, the cam 90 at one revolution an hour and thecam 88 at one revolution every 12 hours. Therefore, the position of thedetents of the cams with respect to the cam follower is proportional tothe time that has elapsed while the mechanical clock movement is drivingthe cams which, of course, is the length of time of a power failuresince the only time the mechanical clock movement 38 drives anything iswhen the power has failed or is purposely cut off.

When power is returned, the coil 110-of the third clutch 42 is energizedsetting up a magnetic field in paramagnetic frame 100. This draws theplate 98 into contact with the frame 100 thus positioning the clutchingsurfaces 102 out of contact with the third meshing gear 48 and intocontact with the disc 104.

With the clutching surfaces 102 out of contact with third meshed gear48, the earns 88 and 90 stop, having rotated to a position whichindicates the total amount of time which elapsed while the power wasoff. In this position of the cams the switch 30 is closed except, ofcourse, if the length of the power failure happens to be 12 hours ormultiples thereof. With the switch 30 closed, current is fed to thewindings 24 of the electric clocks 10 to drive the electric clocks atten times their normal speed as outlined above.

At the same time current is fed through the switch 30 to the coil 111 ofa synchronous motor 113. The output shaft 114 of this synchronous motor113 is coupled by a gear train 116 to the gear 108 fixed to the disc 104so that the gear 108 is driven by the synchronous motor 113. Since thegear 108 is fixed to the cam shaft 86 by the clutching surfaces 102 whenpower is on, this means the earns 88 and 90 are also driven by thesynchronous motor 113.

The gear train 116 is selected so that the synchronous motor 113 drivesthe earns 88 and 90 at nine times their normal speed in acounterclockwise direction. Therefore, when the synchronous motor 14 hasdriven the hands of the systems clocks 10 so that they again read thecorrect time, the synchronous motor 113 will have driven the cams 88 and90 to their normal position, that is, with the cam follower 92 in boththe detents. This opens the switch 30 stopping the flow of current tothe synchronous motor 113 and to the synchronous motors 14. Therefore,the hands of the systems clocks 10 again start keeping the correct timeand the cams 88 and 90 remain in their normal position until there isanother power failure.

Up until now, in the above description, mechanical clock movement 36 hasbeen described as if it runs all the time. If this was the case therewould be serious problems with wear of the mechanical clock movement andthe winding of the mechanical clock movement. The mechanical clockmovement in fact is stopped while the electric power is on and is onlywound when the electric clocks 10 are being corrected after an electricpower stoppage.

The stopping and starting of the mechanical clock movement 36 isaccomplished by moving the end of a flexible shaft 118 in and out ofcontact with the spokes of the main wheel of the escapement mechanism ofthe mechanical clock movement 36 to respectively stop and start themechanical clock movement 36. The flexible shaft 118 up a magnetic fieldwhich draws the paramagnetic arma- 'ture'126 of the solenoid into theenergized coil 124 forcing the flexible shaft 118 in. between the spokesof the main wheel of the escapement mechanism of the mechanical clockmovement 36 thereby keeping the mechanical clock movement 36 stationary.When power fails, the sup ply of current to the coil 124, of course,stops. This dissipates the magnetic field set up by the coil 124 andpermits a spring 128, to pull the core 126 partially out of the coil 124thereby removing the end of the flexible shaft 118 from between thespokes of the main wheel of the mechanical clock movements escapementmechanism allowing the mechanical clock movement 36 to operate.

Like the solenoid 120 the coils 68, 80 and 110 of the electromagneticclutches 38, 40 and 42 are energized by a rectifying bridge circuit 130connected across the 115 volt 60 cycle line for the system clocks 10.When power is on, the DC. supply 130 feeds current in series througheach of the coils 68, 80 and 110 to keep the clutches energized. Whenpower fails, the DC. supply 130 can no longer supply the coils withelectric current and the clutches become deenergized. Therefore,energization and deenergization of the coils 68, 80 and 110 and thesolenoid 120 occur simultaneously so that when power fails themechanical clock movement starts operating at the same time its outputshaft 60 is engaged to drive the first meshed gear 44, and when powerreturns, the mechanical clock movement 36 stops operating at the sametime its output shaft 60 is uncoupled from the first meshed gear 44.

While the mechanical clock movement is driving the hands of the masterclock face 28 and driving the earns 88 and 90, its mainspring isunwinding. Eventually the mechanical clock mechanism would stop if itsmainspring were allowed to unwind completely. Therefore, the. mainspringmust be wound periodically to be sure the mechanical clock mechanismnever runs down. For this purpose, a synchronous motor 132, is employed.The output shaft 134 of the motor 132 is connected to the windingmechanism of the mechanical clock movement 36 and the coil 136 of themotor 134 is connected in shunt with the field coil 111 of thesynchronous motor 113 which drives the earns 88 and 90.

When the synchronous motor 113 drives the earns 88 and 90 with theresumption of power, the synchronous motor 132 winds the main spring ofthe mechanical clock movement 36. The motor 132 is geared to the windingmechanism of the clock so that it will have fully wound the main springof the clock when the synchronous motor 113 drives the detents of thecams under the cam follower 92 to cut off the supply of current to thewindings of both the synchronous motors 113 and 132 to stop both motors.

At times, it is desirable that the master clock and downtime accumulatorsystem be turned off for repairs while the electric clocks 10 continueto keep the correct time. For this purpose a switch 138 is provided tobreak the connection between volt 60 cycle line and the coil 140 of thesynchronous motor 34. In such'a case, it is undesirable to have themechanical clock movement 36 operating since this would interfere withthe repairs. To prevent operation of the mechanical clock mechanism 36at that time, the switch 138 is mechanically linked through a linkage141 to the flexible shaft 118 so as to prevent the end of the flexibleshaft 118 from being removed from between the spokes of the main wheelin the escapement mechanism of mechanical clock movement 36 when theswitch 138 is open.

After the opening of switch 138, and at other times, it is necessary tocorrect the hands of the master clock face 28. To do this a secondsynchronous motor 142 is" provided for driving the hands of the masterclock face 28. The coil 144 of this motor is connected in-seri'es'withthe normally closed switch 138 and a normally open switch 146 acrossthe 115 volt 6O cycle line. When the switch 146 is closed both thesynchronous motors 34 and 142 drive the hands of the master clock face28 through a differential 148. Like in the case of the electric clocks10, with both synchronous motors 12 and 14 driving the hands of themaster clock face 28 the hands move at ten times their normal rate tomake up anyerror which may exist. When the hands of the master clockface 128 again read the correct time the switch 146 is opened manually,thus cutting off current flow through the coil 144 to stop the motor 142so that thereafter the hands of the master clock face 28 are driven atthe normal rate by synchronous motor 34.

When the systems clocks 10 cannot be corrected by the downtimeaccumulator they may be corrected manually by a switch 150. Positioningthe switch 150 in its normally open position connects the coils 24 ofthe motors 16 directly across the 115 volt 60 cycle source of excitationbypassing the control switches 30 and 32 of the downtime accumulator.The systems clocks 10 will thereby run at ten times normal speedirrespective of the position of the earns 88 and 90 until the switch 150is again positioned back into its normal position.

All the electrical motors in the clocks can be turned off by the mainpower switch 152 when it is desirable. However, with the main powerswitch open, the mechanical clock movement 36 will cause the cams 88 and92 to accumulate downtime and will keep the hands of the master clockface 28 indicating the correct time unless the switch 138 is also openedto keep the mechanical clock movement stationary.

If there is a short in the system, the fuse 154 will blow. This, ofcourse, will cut off electricity to all the synchronous motors in thesystem as does opening the master power switch 154. But, here again, themechanical clock movement will accumulate downtime on the cams 88 and 90and will drive the hands of the master clock face to keep them readingthe correct time.

A dial light 156 is connected in shunt with the coil 24 of thesynchronous motors 14 so that it will light when the electric clocks arebeing accelerated.

In the above system, it is very important that the clutches used in thesystem operate correctly and that they use very little power. Thoughmany clutches may be used the preferred type of clutch is shown inFIGURES 2 and 3. In these figures, a clutch plate 160 such as the thirdmeshed gear 48 or the disc 102, is provided with a series of grooves162, completely around its periphery, which are radial with respect tothe axis of rotation for the plate 160. These radial grooves arenumerous and are quite closely positioned as shown in the figure.

Preferably, the clutch plate 160 also has a number of circular grooves164 which are concentric with the axis of rotation of the plate 160 andare positioned so that the radial and circular grooves intersect todivide the peripherial section of the clutch plate into a series ofperfect ring segments.

To engage the clutch plate for the transferral of motion a number ofsoft rubber surfaces 166 are provided. These soft rubber surfaces 166are bands of rubber positioned on arms 168 extending from a plate 170.Also, the portions of the arms 168 about which the bands 166 are wrappedare each locally defiectable, that is to say, independently of all theother portions, in order to accommodate misalignment or unevenness inthe alignment of the arms.

In an operative clutch, such as the clutches illustrated in FIGURE 1,the surfaces shown in FIGURE 2 and FIGURE 3 face each other and areengaged and disengaged. When they are engaged, the soft rubber surfaces166 are positioned against the portion of the clutch plate 170 coveredwith the ring segments. Soft rubber and ring segments have been found toprovide a tremendous grab even when light-weight springs and small coilsare used. It is preferable that the grooves or ridges of the ringsegments be truly radial from and circular with the axis of rotation ofthe plate. Otherwise the plates will move with respect to each otherwhen they are engaged or disengaged. Such movement introduces errorswhich must be avoided.

Above, the preferred embodiment of the present invention has beendescribed. It will be understood that the present invention is notlimited to this embodiment. Therefore, it will be understood that thisis intended to cover all changes and modifications of the inventionherein chosen for the purpose of illustration which do not constitutedepartures from the spirit and scope of the invention.

What is claimed is:

1. In a light weight electromagnetic clutch of the type which is used inclock systems for switching between electric and mechanical drive meansand which has two rotatable members that can be positioned together totransmit rotary motion from one member to the other and can bepositioned apart so that either member can be rotated independently ofthe other, the improvement which comprises:

(a) a surface on the first of the members with a multiplicity of rigidgrooves which are radial with respect to the axis of rotation of saidfirst member and which lie generally in a common plane; and

(b) a plurality of spaced resilient members on the second of the twomembers, said resilient members having substantially flat surfaces whichface the grooves of said first member and which also lie generally in acommon plane whereby the area of said facing surfaces engages acorresponding area of the grooves of the first member substantiallysimultaneously when the two members are positioned together to transmitmotion between the two members.

2. The structures of claim 1 wherein said surface on the first of themembers also has a multiplicity of closely spaced circular grooves whichintersect said straight grooves and whose center is on the axis ofrotation of said first member.

3. The structure of claim 1 wherein said spaced resilient members aresoft elastomeric sleeves positioned around arms extending from saidsecond member.

4. The structure of claim 3 wherein each said arm is locally deflectablewith respect to the other arms so as to accommodate misalignmentsbetween the two members and unevenness of said surface.

References Cited UNITED STATES PATENTS 1,622,261 3/1927 Payne.

2,180,086 11/1939 Kraft 192-107 2,217,529 10/1940 Spase 192 107 X2,299,028 10/1942 Nutt etal 192 107 3,073,424 1/1963 Russell 192- 107x3,096,863 7/1963 Shefke 192 -s4 X 3,233,710 2/1966 Daniels 192-4143,272,290 9/1966 Goddard 192-84 X MARK NEWMAN, Primary Examiner.

ARTHUR T. MCKEON, Examiner.

1. IN A LIGHT WEIGHT ELECTROMAGNETIC CLUTCH OF THE TYPE WHICH IS USED INCLOCK SYSTEMS FOR SWITCHING BETWEEN ELECTRIC AND MECHANICAL DRIVE MEANSAND WHICH HAS TWO ROTATABLE MEMBERS THAT CAN BE POSITIONED TOGETHER TOTRANSMIT ROTARY MOTION FROM ONE MEMBER TO THE OTHER AND CAN BEPOSITIONED APART SO THAT EITHER MEMBER CAN BE ROTATED INDEPENDENTLY OFTHE OTHER, THE IMPROVEMENT WHICH COMPRISES: (A) A SURFACE ON THE FIRSTOF THE MEMBERS WITH A MULTIPLICITY OF RIGID GROOVES WHICH ARE RADIALWITH RESPECT TO THE AXIS OF ROTATION OF SAID FIRST MEMBER AND WHICH LIEGENERALLY IN A COMMON PLANE; AND